Process of desulfurizing metal sulfids.



A. B. FOSTER.

PROCESS OF DESULFURIZING METAL SULFIDS.

APPLICATION FILED MAY 1, I9l5.

Patented Mar. 4, 1919.

Tbsulfur Recovery UNITED STATES PATENT OFFICE.- ARTHUR 1B. FOSTER; or WASHINGTON, DIsTaIcT or coLUMBImAssIeNon. To SULPHUR SYNDICATE, LIMITED, or LoNDoN, ENGLAND, A coaroItATIoN or G EA BaITaIN.

PROCESS OF DESULFURIZING- METAL SULFIDS.

Specification of Letters Patent.

Patented Mar. 4, 1919.

Application filed May 1, 1915. Serial No. 25,259.

v To all whom it may concern:

Washington, District of Columbia, have invented certain new and useful Improvements in Processes of Desulfurizing Metal Sulfids, of which the following-is a specification. I

The present invention relates to the desulfurization of metal sulfids, such as sulfid ores, and provides for the recovery, in elemental form of substantially all the sulfur content thereof. The processis applicable to such oresas contain a considerable amount of so-called feeble atom of sulfur, for example pyrites ores, and also to such ores as do not contain any considerable amount of feeble atom, for example pyrrhotite ore, both these ores frequently contain-. ing more or less copper, or other metal which can be recovered from the desulfurized one, by smelting or other methods.

It has, heretofore been proposed to roast ores in a reducing or non oxldizing atmosphere, in the presence of considerable amounts of steam, to drive off the bulk of the sulfur of the ore either in the form of free sulfur or hydrogen sulfid, or mixtures of these metals, which mayor may not contain more or less sulfate.

It has long been recognized that hydrogen sulfid reacts with sulfur dioxid, under favorable conditions of temperature, to produce I Water and free sulfur, in accordance with the reaction.

This reaction has previously been utilized in various processes, having for their object the recovery of free sulfur by roasting ores.

In my process, a portion of the ore is roasted in the ordinary manner, in any suitable type of ore roasting furnace, which ma or may not be a mechanical furnace, suc as one of the types of furnaces above referred tq, The-roasting of the ore in this manner may be accelerated if desired, by the use of solid, liquid or gaseous fuel,-as has heretofore been proposed, the'result of this step being the production of (a) roasted ore, consisting essentially of oxid (which may contain more or less sulfate, and usually more or less unconverted ore) and (b) gases and vapors containing considerable amounts of S0 The gases and vapors are then passed, (preferably but not; necessarily with the addition ofmore or less moisture, for example steam) through a mass or bed of unroasted ore, which may be pyrites ore, pyrrhotite ore, or the like, which mass or bed of ore is maintained at atemperature, materially above incipient redness, a temperature of 750 to 900 C. being in most instances satisfactory, but the temperature employed (when using an apparatus of the type here illustrated) will necessarily depend upon the melting point of the ore under treatment. It is not my intention to melt or sinter the ore in this step of the process, but it is preferable to malntain the ore as near the sintering temperature as is safely possible, since the reaction takes place much better at higher temperatures. It is possible, even without the addition of steam, to reduce a large part of the sulfur dioxid contained in the roaster gases to free sulfur, perhaps in accordance with the following reaction (2) 2SO +3FeS=5S+Fe O,.

a ed sul d ore. Possibly the following reaction takes place between the steam or mois-' ture and iron sulfid v and the I-LS and free hydrogen thereby produced react with some of the SO present in accordance with reaction (1) above given. Reaction (3) goes on, at temperatures which I have been able to attain in my experiments, much more readily, and very much more completely, than reaction (2), al-

' though probably all these reactions go on simultaneously. \V

The gases leavlng the compartment, in

Y which the ore is treated with the roaster gases, will contain the major portion of the sulfur of the ore, in the form of elemental sulfur, and are then passed, preferably after suitable cooling, through any eflicient type of gas washer or scrubber, such as a Feld tion of the ore will preferably be conducted in a receptacle of considerable height, of which the lower portion is heated, in any suitable manner, to the temperatures above stated, and the hot gases and vapors leaving this portion of the apparatus pass upwardly through a rather deep bed of the ore, in order to impart their heat to the incoming cooler ore. "The ore treated in this step may be only partially desulfurized,

. ore is introduced through the hopper 1,

and may then be conveyed by suitable means into an ore roasting furnace, preferably at or near the top ofthe same furnace, in M which the other oreis roasted, or to some other furnace.

While the process forming the subject matter of my present invention may be carried out in various forms of apparatus, I have shown in the annexed drawing, a form of apparatus which may be used. Said drawlng shows diagrammatically, a

.vertical section of a suitable form of apparatus.

Referring to said drawing, a part of the into the upper compartment of an ordinary multiple shelf-roaster 2 provided with suitable rabble arms 3, carrying rabbles, the

roasted ore being discharged through the spout 4 to a suitable conveyer 5,.the rabble arms being carried by the revolving shaft 6, the ore passin downwardly over the successivehearths, g, 8, 9, 10, 11 and 12, all in a manner well understood in the art.

To the gases and vapors leaving the rgaster, throughthe Qfiue 13, I may add steam through the pipe 14, the gases then entering the chamber 15, having a false bottom 16 to support the bed of 'granular fire 17. The lower portion of this bed of ore is maintained at a temperature above incipient redness, preferably above 700 (3., and I prefer to maintain the ore in the bottom of this bed- 17 of are as recovery of sulfur.

near the sintering point of the ore as it is possible to do, without actually sintering, a temperature Oi850 to 900 (3., being suitable for many kinds of ore. This heating may be accomplished in any suitable manner, electric heating being cited as one convenient mode. From this charge, ore is preferably withdrawn, either continuously or intermlttently, for example by the passage 18, containing a gate 19, while fresh ore is introduced through the hopper 20.

The ore introduced may be first heated to drive off any feeble atom of sulfur, but this is usually neither necessary nor. desirable. The bulk, of the feeble atom may be distilled in the upper part of chamber 15.

To insure proper travel of the gases and vapors through the system,- a pump or blower 21, or other device may be used. The gases from pipe 22 are carried offto anysuitable device, as above noted, for th The reactions in the gases may not be complete until the gases and vapors reach the gas washer.

I prefer to introduce all the air for the ore roasting operation at 23, but if desired a part of the air may be introduced to one or more of the compartments higher up.

In carryingout the process with such an apparatus as is here shown, the temperature of the ore in the chamber 15 should preferably be kept near to, but slightly below, the temperature of incipient fusion.

What I claim is 1. A process ofdesulfurizing metal sulfids, which comprises maintaining a bed of metal sulfid,ata temperature at which iron exercises a greater afiinity for oxygen than does the sulfur of sulfur dioxid, and passing gases containing sulfur dioxid through said bed of metal sulfid.

2. A process of desulfurizing metal sulfids, which comprises maintaining a mass of metal sulfid, at a temperayure materially above incipient redness, ,and maintaining gases containing sulfur dioxid in intimate contact therewith, until the majorpart of said sulfur dioxid is reduced.

3. A process of desulfurizing which comprises roasting metal sulfid in the presence of air to produce gases containing sulfur dioxid, and passing said gases in contact with a body of metal sulfid, at least a portion of which is at a temperature materially above incipient redness, while maintainin contact between said gases and said meta sulfid until at least the major portion of the sulfur dioxid therein is reduced.

at a temperature at which the sulfur dioxid;

willreact with'the said sulfid and contact-1 ing said gases and thesulfid at the temper-J A ature described until at least the major portion of the sulfur dioxid is reduced.

5. The improvement in the process of de- -sulfurizing metal sulfids, which comprises jor portion of the sulfur dioxid is reduced.

6. A process of desulfurizing metal sul'fids, which'compri-ses roasting metal sulv fid to produce gases contalning sulfur dioxid, treating metal sulfid, at a temperature of above 7 00 0., with the gases containing sulfur dioxid produced in said first step until at least the major portion of the sulfur dioxid is reduced.

* 7. A process of desulfurizing metal sulfids which comprises roasting metal sulfid to produce gases containing sulfur dioxid, treating metal Sn (1, at a temperature of above 700 (3., wit the gases containing sulfur dioxid produced in said first step, and until at least the major portion of the sulfur dioxid of said gases is reduced, thereafter further roasting the solid product of the second step.

8. process of desulfurizing ore which comprlses contacting sulfid ore with gases containing sulfur dioxid and moisture, at a temperature at which theemetal of the sulfid ore has a greater aifinity for oxygen than for sulfur.

9. A process of desulfurizing ore which comprises treating sulfid ore with gases contaming sulfur dioxid and moisture, at a a temperature materially above i-nclpient redness until at least a material part of the sulfur dioxid is reduced.

10. A process of desulfurizing which comprises roasting metal sulfid in the pres ence of air to produce gases containing sul-- fur dioxid and passing said gases, together with moisture, into contact with a body of .metal sulfid, at least a portion of which is at a temperature at which the metal of the said sulfid is capable of reducing sulfur dioxid. 11. A process of treating gases contain ing sulfur" dioxid, which comprises passing the same with moisture, into and through a ,body of metal sulfid, of which at least a part is maintained at a temperature at which the sulfur dioxid will react with the said sulfid. I

12. The improvement in the process of desulfurlzing metal sulfids, which comprises treating metal sulfid with gases containing sulfur dioxid and steam at a temperature at which sulfur dioxid is capable of'des'ulfurizing said sulfid.

13. A process of desulfurizing metal sulfids which comprises roasting metal sulfid and thereby producing gases containing I sulfur dioxid, maintaining contact between metal sulfid, held at a temperatureof above 700 0., and gases containing steam and. the

sulfur dioxid produced in said first step until at least the major portion of said sulfur dioxid is reduced.

-. 14. A process of desulfurizing metal sulfids which comprises roasting metal sulfid 15. A process which comprises passing gases containing sulfur didxid in an upward direction through a deep bed of-material containing metal sulfid, at least a part of said .bedbeing maintained at a temperature above 700 (1, while maintaining contact between said sulfid at the stated temperature and said gases, until at least the major portion of the sulfur dioxid in said gases is reduced.

16. A process which comprises passing gases containing sulfur dioxid-and water vapor in an upward direction through a deep bed of material containing metal sulfid, at least a part of said bed being maintained at atemperature above 700 0., while maintaining contact between said sulfid at'the stated temperature and said gases,

until at least the major portion of the sul- 1 oxygen greater than that exercised by sula fur for oxygen, and passing gases contain ing an oxid of sulfur through said'bed 'of metal sulfid, and maintainingthe said OXlCl of sulfur in contact with said metal sulfiduntil at least the major portion of the oxygen content of said oxid of sulfur combines with the metal of saidmetal sulfid. I

18. The step of reducing sulfur oxids by maintaining persistent contactbetween the gases containing oxid of sulfur and a metal sulfid, at a temperature atwhich the metal Y of said sulfid has a greater afinity for the oxygen of said oxid of sulfur than for the 'sulfur of the metal sulfid, until at least a material amount of the oxid of sulfur is reduced. p

19. The step of reducing sulfur oxids by maintaining persistent contact between the gases containing moisture and oxid of sulfur and a metal sulfid, at a temperature at which the metal'of said sulfid has a greater afiinity for the oxygen of said oxid of sulfur than for the sulfur of the metal sulfid, until at least a material amount of the oxid of sulfur is reduced.

I 20. The herein described process which comprises oxidizing the metal content of a metal sulfid, by the oxygen content of an oxid of sulfur.

21. In desulfurizing metal sulfid the im-- provement which comprises maintaining a maswf solid heavy metal sulfid at a temperature at which at least one of the metals thereof has greater aifinity for the oxygen of sulfur .oxicls than does sulfur, and bringing into contact with said sulfid, gases conlo taining an oxid of sulfur and retaining said materially less percentage of oxids of sulfur 5 than did the gases before contact with said metal sulfid.

In testimony whereof I aflix my signature.

ARTHUR B. FOSTER. 

